The problem is that rally there is very little actual empirical research going on. There are a few AES papers including a sociologically interesting

"Jihad" between high res PCM (Meridian and the Acoustic Renaissance for Audio bunch) and DSD proponents that

get pretty heated and lots of trade show "demonstrations". The problem is that there are few empirical studies rigorously attempting to

study audible differences. The two papers I cited earlier "Gustavino and Pras" and "Meyer and Moran" reaching rather different conclusions

there is also Blech and Yang DVD-Audio versus SACD: Perceptual Discrimination of Digital Audio Coding Formats which compares er

DSD and PCM but is not definitive.

You personal case is interesting but what you hear differently is a (so far) mystery as nobody can replicate it, I tried and failed, do you

have unusually sensitive ears, are you unconsciously picking up some tiny artifacts that nobody else can (this happened in one of

the early MP3 codec tests where a chap with a specific hearing loss at a certain frequency range was able to hear very slight

encoding artifacts that others missed) who knows ?

Can you recruit 20 or so friends and get them to try with the same setup ? That would be very telling !

I've tempted a musician relative into trying it out, but he would have different audio interface and headphones. Other than that I don't have a means to assemble a proper sample group. I think I can safely say my hearing is sensitive in a way that's different from others. I've always had a low pain threshold--always plugged my ears when in the NYC subway, pretty much stayed away from big rock concerts, still find the movies way too loud, etc.

On these ABX's I have found hearing fatigue to be a serious impediment. It took a lot of patience to wait between trials on many of the pairwise tests, but when I started rushing I lost acuity after just 5 rounds or so.

I wonder if the foobar player + files as produced by knowledgeable members here gives rise to an opportunity to crowdsource the testing. Maybe a game structure wrapped around the hearing tests.

I do confess some surprise at seeing [apparently] so much testing and marketing around mere cables, when basic issues like MP3 formats are dominating the market.

Interesting, if irrelevant analogy. The ability of a trained music professional to discern pitch with precision beyond the general populace is well documented. However, there is also a wide range of that ability within the untrained populace, which I find far more fascinating. Pro's aren't the only ones with precision pitch. But that's not to denigrate your abilities at all, it's an honor to have a classical composer here!

No one knows for sure, of course, but I wouldn't put the correspondence here down to pitch detection per se, so much as to something like "Subtle Pattern Detection In Dense Aural Information Contexts". Hearing the flatness of the oboe player is actually the easy part. More difficult is picking the oboe line out of the full orchestral texture, particularly in instances where the flutes and violins are playing the same melody, and the oboe is far from the loudest component. Conductors are adept at mentally separating out the individual contributing components of the sound waves which reach their ears, and they have a very powerful mental model of what each component, plus the combined whole, *should* sound like. Departures from that model (discrimination skill) set off an alarm in the conductor's mental analysis of what s/he's hearing.

The thing about trying to get definitive results out of an ABX test is that you have to get all variables under tight control, then you have to collect a lot of data from randomized subjects. This is not as easy as the whole Foobar/ABX concept might make it seem. We'd all like to run a couple of ABX tests, get the data and call it a day.

The problem I see with ABX testing of different files with the goal to determining the audibility of different bit rates and depths is:

1. Source material. Assuming we don't use digitally synthesized test signals, we need to sample analog first. There are three general methods, the first two are to sample high-rate then down-sample to obtain the low-rate file, sample low rate then up-sample to obtain the high-rate file. The problem with both is they involve up or down sampling, which is a variable (different algorithms, etc), and could have an impact. The third method is to sample the analog original simultaneously with two ADCs running at different rates, but identical in every way possible. The problem with that is that of necessity, the lower-rate ADC will have a different anti-aliasing filter than the high-rate ADC, which could be considered either a variable or part of the fingerprint. What you end up with isn't quite a definitive bit rate comparison, but a definitive comparison of the results of a specific DAC running at different rates, which when you get down to it, is not quite unassailable, but probably better than many at least some of the prior art.

2. The second half of the chain also contains unknown elements. DACs performance differ significantly, which imposes another unknown variable. What happens after the DAC is also a bit unknown, especially when you're crowd-sourcing, but would end up being a bit of random statistical noise rather than a bias.

So what we would need to do is set up tests for each of several conditions, collect data from several dozen trials with as many testers for each condition, then analyze what we have. Clearly, that's not a project undertaken lightly, though it's fascinating to consider the crowd-sourcing possibilities. If whoever was doing the project could be funded enough to generate test files that were carefully done and with the variables known, then distributed them, we might actually have something here. But until then, I wouldn't put a whole lot of confidence in the data obtained from casual ABX testing, though it's clearly far more relevant than casual sighted A/B testing.

No one knows for sure, of course, but I wouldn't put the correspondence here down to pitch detection per se, so much as to something like "Subtle Pattern Detection In Dense Aural Information Contexts". Hearing the flatness of the oboe player is actually the easy part. More difficult is picking the oboe line out of the full orchestral texture, particularly in instances where the flutes and violins are playing the same melody, and the oboe is far from the loudest component. Conductors are adept at mentally separating out the individual contributing components of the sound waves which reach their ears, and they have a very powerful mental model of what each component, plus the combined whole, *should* sound like. Departures from that model (discrimination skill) set off an alarm in the conductor's mental analysis of what s/he's hearing.

I would assume that a variant of the discrimination skill should, ideally, be at work within each player such that they hear the composite and adjust to "fit", is that right? My limited experience with playing and singing in groups always seem to reveal good players as either "soloists" who just play their best, and real group members who try to play with the group. It would seem like some sort of reverse-discrimination skill would work the best.

I would assume that a variant of the discrimination skill should, ideally, be at work within each player such that they hear the composite and adjust to "fit", is that right? My limited experience with playing and singing in groups always seem to reveal good players as either "soloists" who just play their best, and real group members who try to play with the group. It would seem like some sort of reverse-discrimination skill would work the best.

Just musing about music...

Definitely agree with that. Each player has an internal mental model of what the music is supposed to sound like. Pattern-matching across from the internal idealized form of the music to one's own playing, and to the playing of others, should be going on continuously. In order for an orchestra to play Richard Strauss well, the pitch, beat, and timbre pattern-matching has to be exquisite. Jazz ensembles highlighting their improvisation skills have fewer fellow instruments to deal with, *but* they are matching not only the above, but also melodic and rhythmic ideas; when one player selects a note not normally in the key, or turns the melody in an unexpected direction, the others notice [pattern-matching] and adjust their playing to match, including taking off from the one new idea into several--pure genius when done well, with mutually responsive players in the group.

For some settings, the 'together' aspect gets a bit more complicated. The bigger the opera star, for example, the more likely the final product is going to be a collaboration between the mental models of the singer and the conductor--including some serious tug-of-war in rehearsals, and even in performances. When Pavarotti hit the climactic note, *only* he himself determined when that note would end, and how. At this level it's an even deeper game: they have multiple models of what's going to happen, and are adjusting to multiple contingencies on the spot. No one sweats harder than an opera conductor, in this respect, I'd say.

The thing about trying to get definitive results out of an ABX test is that you have to get all variables under tight control, then you have to collect a lot of data from randomized subjects. This is not as easy as the whole Foobar/ABX concept might make it seem. We'd all like to run a couple of ABX tests, get the data and call it a day.

The problem I see with ABX testing of different files with the goal to determining the audibility of different bit rates and depths is:

1. Source material. Assuming we don't use digitally synthesized test signals, we need to sample analog first. There are three general methods, the first two are to sample high-rate then down-sample to obtain the low-rate file, sample low rate then up-sample to obtain the high-rate file. The problem with both is they involve up or down sampling, which is a variable (different algorithms, etc), and could have an impact. The third method is to sample the analog original simultaneously with two ADCs running at different rates, but identical in every way possible. The problem with that is that of necessity, the lower-rate ADC will have a different anti-aliasing filter than the high-rate ADC, which could be considered either a variable or part of the fingerprint. What you end up with isn't quite a definitive bit rate comparison, but a definitive comparison of the results of a specific DAC running at different rates, which when you get down to it, is not quite unassailable, but probably better than many at least some of the prior art.

I found out right away when I opened the iZotope SRC that "upsampling" was a procedure with plenty of choices right there, AND trade-offs between, them, AND differing recommendations about how to use the settings. And then all over again with "downsampling", so possible outcomes get pretty deep pretty quickly. I bolded and red-ed your line above, because it goes to just those points. I'm not sure, even, what an experimental design which *entirely* isolated ONLY the effects of sample rate would have to look like. As soon as one is playing back at different sample rates, the playback chain is of necessity different, with all the attendant possible effects in the elements of the playback chain. [As you address below]:

2. The second half of the chain also contains unknown elements. DACs performance differ significantly, which imposes another unknown variable. What happens after the DAC is also a bit unknown, especially when you're crowd-sourcing, but would end up being a bit of random statistical noise rather than a bias.

This is getting really speculative, but--there are meta-analysis techniques which *might* allow a [well-resourced] researcher to cross-match the results of many thousands of experiments on non-identical equipment, to try to sort out which variables are more likely to be responsible for which results. There would need to be a wide variety of well-designed test files--that part would have to be common across trials--which would include both test tones designed for the trials, and a wide variety of program material. The only thing that potentially helps the researcher get something out of this morass of data is the very large numbers of trials for each of the test files.And of course, there would need to be some demographic data (like age), and maybe even a short frequency-range hearing test worked into the front end of the game somehow.

So what we would need to do is set up tests for each of several conditions, collect data from several dozen trials with as many testers for each condition, then analyze what we have. Clearly, that's not a project undertaken lightly, though it's fascinating to consider the crowd-sourcing possibilities. If whoever was doing the project could be funded enough to generate test files that were carefully done and with the variables known, then distributed them, we might actually have something here. But until then, I wouldn't put a whole lot of confidence in the data obtained from casual ABX testing, though it's clearly far more relevant than casual sighted A/B testing.

Getting the design right would be an awful lot of work, as well as connecting theory to methodology in rigorous ways. But, I have to say, if I were a journal editor looking at a submitted paper with this sort of innovative testing approach, and I thought it was done well (within the boundaries of what's possible), there's **no way** I would not accept it for the centerpiece of an upcoming issue.

HydrogenAudio forum does lossy perceptual codec public listening tests - high bit rates were given up long ago due to statistical insignificance of the public test results as the codecs, algorithm tunings improved

HydrogenAudio forum does lossy perceptual codec public listening tests - high bit rates were given up long ago due to statistical insignificance of the public test results as the codecs, algorithm tunings improved

As in, test files posted in the forum for people to try? Lossy perceptual codecs are definitely the most important area to address, from both business and musical points of view. Over 90% of my students now say they do the majority of their listening on Pandora, and I get my own widest/most interesting exposures to new music from YouTube, despite the, uh, 'quality' of the accompanying audio stream. I wouldn't know about Yasutaka Nakata without YouTube, so I'm grateful, I really am.

But........when *I* was an undergraduate, everyone I knew had or wanted a component stereo system with the best pieces they could afford. My roommate freshman year had a true quadraphonic system, and a Nakamichi cassette deck with a per-tape customizable bias control. We *cared* deeply about music quality, and we were not anomalies among consumers, stereo component shops were everywhere.

But........when *I* was an undergraduate, everyone I knew had or wanted a component stereo system with the best pieces they could afford. My roommate freshman year had a true quadraphonic system, and a Nakamichi cassette deck with a per-tape customizable bias control. We *cared* deeply about music quality, and we were not anomalies among consumers, stereo component shops were everywhere.

I was an undergraduate in the UK back in the mid to late 70s all my friends had record players most of them were part of music centers, only me and one other had separate TTs and by the time I graduated (1979) two channel HiFi was starting to decline into a small niche, most people I knew then just had something to play records or tapes on. The paradox being that in the mid 80s with CD being adopted and vinyl slowly losing market share people got better playback quality whether they wanted it or not !

The problem lies with getting good original source files, which would be expensive. You need an unassailable capture system, studio, and frankly, interesting music. Getting the "crowd" to test and submit is easy, and managing the data is, well, the job. But, this falls into the "no bucks, no Buck Rogers" class. This is a university-level or Harmon-level project, to do it right. Yes, any editor would take it, but they won't pay up for the research, it has to come from a higher source, hopefully one with a more noetic interest than a commercial one.

The problem lies with getting good original source files, which would be expensive. You need an unassailable capture system, studio, and frankly, interesting music. Getting the "crowd" to test and submit is easy, and managing the data is, well, the job. But, this falls into the "no bucks, no Buck Rogers" class. This is a university-level or Harmon-level project, to do it right. Yes, any editor would take it, but they won't pay up for the research, it has to come from a higher source, hopefully one with a more noetic interest than a commercial one.

Did anyone else just get a survey request from Sony? This would be within the last month. I answered questions specifically about music formats both delivered on disks and through direct download. My friend at the Japan Times says the Asian music markets are still more focused on disks than on pure information goods, and it kind of sounded like they were fishing for hope that their in-store disk-based retail markets would survive beyond the CD. **I** hope they do, but who knows.